1. Field of the Invention
The present invention relates to a hydraulic brake apparatus for use as, for example, a brake apparatus of a vehicle.
2. Description of the Related Art
A conventional hydraulic brake apparatus includes a tandem brake master cylinder having a rod piston and a floating piston, the rod piston moving in response to a brake-operating member such as a brake pedal, and the floating piston moving in response to the rod piston; a separation valve provided in a hydraulic brake circuit connecting the brake master cylinder and a brake wheel cylinder, the separation valve being able to establish and shut off communication between the brake master cylinder and the brake wheel cylinder; a pressure control valve unit for controlling fluid pressure to be supplied to the brake wheel cylinder from an external fluid-pressure supply source while the separation valve is in a shutoff condition; and a stroke simulator mechanism for allowing an idle stroke of the rod piston and an idle stroke of the floating piston while the separation valve is in the shutoff condition (during an idle stroke, no pressure is generated in the brake master cylinder) so as to ensure a stroke of the brake-operating member in accordance with an input load to the brake-operating member (see, for example, Japanese Patent Application Laid-Open (kokai) No. 10-167042).
The stroke simulator mechanism described in the above publication is set such that an idle stroke of the rod piston, which moves in response to the brake-operating member such as a brake pedal, and an idle stroke of the floating piston, which moves in response to the rod piston, can be performed sequentially and stepwise. Thus, upon completion of the idle stroke of the rod piston, the idle stroke of the floating piston may start. In this case, sliding resistance associated with start of the idle stroke of the floating piston may generate shock, thereby impairing an operator's feeling of operating the brake-operating member.
The stroke simulator mechanism appearing in the above publication is also set such that an idle stroke of a simulator piston can be performed subsequent to the idle stroke of the rod piston and the idle stroke of the floating piston, which moves in response to the rod piston. Thus, upon completion of an idle stroke of the floating piston, an idle stroke of the simulator piston may start. In this case, sliding resistance associated with start of an idle stroke of the simulator piston may generate shock, thereby impairing an operator's feeling of operating the brake-operating member.